Human skin is subject to certain aging processes, some of which are attributable to intrinsic processes (e.g. chronoaging) and some of which are attributable to exogenous factors (e.g., photo-aging). In addition, temporary or lasting changes to the skin can occur, such as acne, greasy or dry skin, keratoses, rosacea, light-sensitivity, inflammation, erythemas, and allergic or autoimmune-reactive reactions, such as dermatosis and photodermatosis.
The consequences of the above can include thinning of the skin, weaker interlacing of epidermis and dermis, and a reduction in the number of cells and the supplying blood vessels. This often results in the formation of fine lines and wrinkles, and pigment defects can occur.
Retinoids have been used for treating skin conditions caused by intrinsic aging, exogenous factors, or skin diseases. Specifically, retinol has been widely used for treating acne and for reducing the appearance of wrinkles, fine lines, stretch marks, and cellulite.
However, despite the beneficial effects of retinoid treatment, retinoids can be irritating. This side effect restricts the use of retinoids.
It is therefore an objective of this invention to provide novel retinoid compositions and methods for the treatment of above-mentioned skin conditions that avoid the adverse effects of retinoid administration. In particular, it has been found that control of the retinoid liberation rate from a cosmetic composition, for example by controlling the polarity of the ingredients in the composition, results in increased retinoid activity and decreased retinoid irritation. We have unexpectedly observed that combining a non-polar emollient with a polar emollient within a range of desirable weight ratios in a retinoid composition significantly reduces the skin irritation of the retinoid and enhances the efficacy of the retinoid.